Why are people so quick to cast big doubts on cdkeys and other sellers when virtually all of the keys they are selling (at least for Xbox) make perfect sense to be sold this way? It seems like pretty much every single game was one that came in a retail combo with a system. There are tons of people in the trading forums selling similar keys. These were probably stripped from those bundles in other countries for various reasons.
There's tons of sites selling UV codes, product keys, etc. and not all of them are bad or even shady. I don't know exactly where CDKeys fits on the moral and ethical scale, but just because they have creative ways of finding and selling a product does not necessarily make them bad.
Also, if key sites like CDKeys were really that subversive, it seems like Microsoft and publishers would definitely be tightening up how they use and distribute and validate keys.